chore(prisma): 新增 audio_source 字段 migration (20260715)

server/prisma/migrations/20260715_add_audio_source/migration.sql

Co-Authored-By: Claude <noreply@anthropic.com>

server/prisma/migrations/20260715_add_audio_source/migration.sql

@@ -0,0 +1,9 @@
+-- 给 BookChapter 加 audioSource 字段，区分完整异步生成 vs on-demand 同步合成
+ALTER TABLE `BookChapter` ADD COLUMN `audioSource` VARCHAR(20) NULL;
+
+-- 已有数据回填：有合法音频（且非 /uploads/）的标记为 'full'；空标记为 NULL
+UPDATE `BookChapter`
+SET `audioSource` = 'full'
+WHERE `audioUrl` IS NOT NULL
+  AND `audioUrl` != ''
+  AND `audioUrl` NOT LIKE '/uploads/%';